Analysis of the recombination-integration sites in the nondefective Ad2-SV40 hybrid viruses is continued. The sequence analysis of the common end point in the Ad2 plus ND2 and Ad2 plus ND4 is completed. The sequence analysis at and near the rec/int site at the variable end point in Ad2 plus ND3 is completed. The segment of DNA which encodes the start of the fiber gene has been identified. It lies about 230 nucleotides downstream from the site of integration of SV40 sequences in the nondefective hybrid virus Ad2 plus ND1. DNA sequence analysis shows that only one reading frame is open and only one AUG is present within the reading frame. From the sequence it could be predicted that a 17-long T1 oligonucleotide should be present in fiber mRNA near the 5' end of the coding region. This oligonucleotide has been identified as part of a fragment of fiber mRNA which can be protected by 80S ribosomes. In a separate experiment we have determined the approximate location of the site at which the leader sequence becomes joined to the main coding region of the fiber mRNA.